Question 1068458
Linear function means the relation of f(x) to x has  x raised to the first power.
Thus, we can write:
    f(x) = mx+b
—
f(-1/2) = -7  —>   -7 = m*(-1/2) + b    (1)
f(1) = -3  —>         -3 = m*(1) + b         (2)
—
Subtract (2) from (1) to get one equation with just 'm':

                              -4 = -(3/2)m
                                  m = 8/3
—
Plug 8/3 in for 'm' in  (1)  (or (2)) and solve for 'b':
                               -7 = (8/3)(-1/2) +b
                                   b  = -17/3
—
Now we have:
                         {{{ f(x) = (8/3)x - 17/3 }}}

—
Just plug in x=-3 and you'll have the answer.  
I got  -41/3.